1. Field of the Invention
The present invention relates to a method and a device for winding a magnetic tape, such as winding a magnetic tape of prescribed length from a source roll of a magnetic tape to a small tape winding body, rewinding a magnetic tape from a tape winding body to another tape winding body, winding a magnetic tape of large width for a source "roll", and winding a magnetic tape of large width to a plurality of tape winding bodies while slitting the tape.
2. Background of the Invention
A process of manufacturing a magnetic tape such as an audio casette tape, a video cassette tape, a memory tape or a broadcasting video tape includes a step of winding a magnetic tape of prescribed length from a source roll of a large-length tape to a small tape winding body such as a reel and a hub, a step of rewinding a magnetic tape from a tape winding body to another tape winding body, a step of winding a magnetic tape of large width as a source tape, a step of winding a magnetic tape slit from another magnetic tape, and so forth. When the magnetic tape is wound on the tape winding body in the process of the winding or the rewinding, the tape may vibrate in the direction of the thickness of the tape and this vibration can fluctuate due to the physical properties of the magnetic tape and those of the tape winding body so that each side edge of the tape wound on the winding body is unneatly overlaid on itself. The higher that the speed of the winding is, the more unneatly the side edge is overlaid on itself.
A magnetic tape whose side edge is unneatly overlaid on itself as described above has problems that the external appearance of the wound tape housed as a commercial product in a magnetic tape cassette is bad. Furthermore, the side edge is likely to be damaged resulting in various troubles such as the deterioration of the electromagnetic converting properties of the tape. The unneat overlaying is a serious drawback, particularly for a magnetic video tape for high-density recording, because an audio signal or a tuning signal is recorded near the side edge of the tape. For these reasons, in a conventional process of manufacturing a magnetic tape, the wound states of all magnetic tapes are visually inspected or the like after a winding process or a rewinding process. Since the inspection takes much time and money, the inspection is a major disadvantage in the magnetic tape manufacturing process.
Conventional systems, which are shown in FIGS. 1 and 2 and which accomplish what is called neat winding, have been adopted to wind a magnetic tape of low neat-winding yield in order to improve the wound state of the tape to reduce the necessity of its inspection. FIGS. 1 and 2 show perspective schematic views of tape winding bodies 2 and the vicinity thereof.
In the conventional system shown in FIG. 1, an endless flexible belt 11 made of rubber, polyimide or the like and rotatably supported by rollers 12, 13 and 14 is revolved together with the magnetic tape T and elastically pushes the magnetic side of the tape under relatively high pressure in the radial direction of the tape winding body 2 to neatly wind the tape.
In the conventional system shown in FIG. 2, a belt 15 made of a relatively soft nonwoven fabric or the like is provided between one flange of the tape winding body 2 and one side edge of the magnetic tape T to push the side edge of the tape T under relatively high pressure while the belt is supported by a roller 17 or the like and wound at a low constant speed from a belt send-out member 16 to a belt winding member 18 so as to neatly wind the tape.
However, since the belts 15 are placed in direct contact with the magnetic tape T in the above-mentioned system, there are various problems that the magnetic layer of the tape T is worn or the fibers of the nonwoven fabric come off to locally hinder recording on the tape T, inappropriate pressure acts to deform the tape or damage its side edge, and so forth. For that reason, the system does not function properly. In addition, since the wear and tear of the neat winding system is large, it has disadvantages with regard to its cost and maintenance as well. The constitution of each of the system needs to be such that the tape winding body 2 is moved between at least a working position and a non-working position when it is replaced. The constitution makes a magnetic tape winding device complicated and renders it relatively time-consuming to replace the tape winding body 2. The period of time required for the movement of the tape winding body 2 hinders the enhancement of productivity.
Two systems for winding a magnetic tape for a cassette are used today. One of them is an open winding system in which the tape is neatly wound and then inserted into the cassette as so to be finished product. The other is an in-cassette winding system which is also called C-O winding system or V-O winding system and in which the tape is wound at the final stage of assembly of the cassette.
As for the in-cassette winding system, as shown in FIG. 3, the cassette 23 without the magnetic tape is first assembled, an outgoing tape winding body 2 and an incoming tape winding body 3 which are coupled to each other by a leading tape 10 are inserted into the cassette 23 and screws are tightened so as to provide a unfinished product generally called V-O, C-O or the like. In the unfinished product, the leading tape 10 is partly pulled out by an in-cassette winder and cut in half. The front end of the magnetic tape T is spliced to one cut-off end of the leading tape 10 whose other cut-off end is held a suction member 22. The tape winding body 2 having the leading tape spliced to the magnetic tape is rotated to wind the magnetic tape on the body 2 by a prescribed length. The magnetic tape T is then cut off. The rear end of the magnetic tape T wound on the winding body 2 is then spliced to the other cut-off end of the leading tape 10, thus finishing the product. Since the wound state of the magnetic tape T entirely depends on the physical properties of the tape T and the accuracy of the assembly of the cassette 23, the wound state cannot be well controlled. For that reason, the yield of well-wound magnetic tapes is low. In order to increase the yeild, a roller 24, shown in FIG. 4, having an upper and a lower flanges 25 has been provided on a trial basis to apply a force to the magnetic tape in the direction of its width to push the tape T sideward. However, if the force is strong, the side edge of the tape is more likely to be damaged. If the force is weak, it hardly serves to neatly wind the tape. All in all, no effective means have been available to improve the wound state of the tape.
Meanwhile, a magnetic tape winding device was recently proposed in the Japanese Patent application (OPI) No. 51642/86 (the term "OPI" as used herein means an "unexamined published application"). In the device illustrated in FIG. 5, a winding drive shaft 30 is removably coupled to the winding hub 41 of a winding reel 42 comprising the hub and a flange 42. At least one magnet 31 is provided to face the wound side edge of a magnetic tape across the flange 42 while the tape is wound on the reel 40 so as to improve the wound state of the tape. However, the magnet 31 provided around the shaft 30 has a problem that the wound state of the tape is worse at its central portion near the winding hub 41 than at the peripheral portion of the tape. That is because the form of the magnet 31 is limited by the shaft 30. The magnet 31 is made annular so that the directions of the lines of magnetic force thereof are nonuniformly distributed near the central portion of the winding reel 40 due to the hollow central portion of the magnet. The magnetic flux density near the center of the reel 40 is so low that the magnetic force which pulls the magnetic tape T toward the flange 42 is unstable and weak at the initial stage of the winding of the tape. There has been disclosed in Japanese Patent application (OPI) No. 16886/86, and Japanese Utility Model Applications Nos. 48899/86 and 48900/86, combined into U.S. Patent Application Ser. No. 8040, filed Jan. 29, 1987, a tape winding device in which a magnetic field is applied in the direction of the thickness of the tape.
Further, it has been impossible to use the device shown in FIG. 5 with a take-up reel which has no flange. Further, at present, the magnet actually used is generally made from alnico or ferrite. When a good wound state is to be obtained with using such a magnet, it has been disadvantageous in that the magnet is unsuitably large in size to thereby require a large installation and a high cost.